Field of the Invention
The present invention relates to an imprint apparatus, an alignment method, and a method of manufacturing an article.
Description of the Related Art
An imprint technique can form a fine pattern, and is coming into practical use as one of lithography techniques for volume production of magnetic storage media and semiconductor devices. As disclosed in Japanese Patent No. 4185941, an imprint apparatus which employs the imprint technique forms a pattern on a substrate such as a silicon wafer or a glass plate using a mold (die), as an original, on which a fine pattern (unevenness) has been formed. The imprint apparatus, for example, coats the substrate with a light curable resin (for example, an ultraviolet-curing resin), and molds the resin using the mold. The resin is irradiated with light (for example, ultraviolet light) to be cured, and then the mold is separated from the cured resin, thereby forming the pattern of the resin on the substrate.
The imprint apparatus adopts the die-by-die alignment scheme or the global alignment scheme as a scheme of alignment between a substrate and a mold. In the die-by-die alignment scheme, for each of a plurality of shot regions on the substrate, an alignment mark on the substrate and an alignment mark on the mold are optically detected to correct a shift in positional relationship between the mold and the substrate. The global alignment scheme is an alignment scheme of correcting the shift in positional relationship between the mold and the substrate based on the positions of all shot regions determined by performing statistical processing on the detection result of alignment marks which have been formed in some representative sample shot regions. As an alignment scope which detects the alignment marks, a TTM (Through The Mold) scope is used in the die-by-die alignment scheme, whereas an OA (Off Axis) scope is used in the global alignment scheme.
The imprint apparatus is required to measure the position of the mold in advance. In the die-by-die alignment scheme, the alignment mark on the substrate and the alignment mark on the mold should come into the field of view of the alignment scope. To achieve this, the position of the mold needs to be obtained in advance (prealignment of the mold). The position of the mold also needs to be obtained in advance in the global alignment scheme because a positional shift in the mold when bringing the resin on the substrate and the mold into contact with each other leads to a decrease in overlay accuracy.
In the prealignment of the mold, the alignment scope first detects the alignment mark on the mold. Next, the alignment scope detects the alignment mark on the substrate or a reference mark arranged on a substrate stage while the X-Y position of the alignment scope is fixed. Then, the relative position between the alignment mark on the mold and the alignment mark on the substrate or the relative position between the reference mark and the alignment mark on the mold is obtained. Such prealignment of the mold takes much time, and thus becomes a factor to reduce the throughput of the imprint apparatus. Particularly, in the imprint apparatus, in addition to the need to change molds regularly, a shift in the alignment mark on the mold is large and thus the alignment mark on the mold easily falls outside the field of view of the alignment scope. Therefore, the prealignment of the mold has a great influence on the throughput of the imprint apparatus.